&DRIFT: PLOT-FIELD


functions

  All functions in the description of the PLOT command (f1, f2 ... f6)
  may depend on the following set of variables:

  ------------------------------------------------------------------------
  Symbol          Meaning                       Note
  ------------------------------------------------------------------------
  X, Y, Z           Position                    R, PHI for polar cells
  EX, EY, EZ, E     E-field at (x,y,z)          ER, EPHI for polar cells
  BX, BY, BZ, B     B-field at (x,y,z)          only if there is a B-field
  VDX, VDY, VDZ, VD Local drift velocity        VDR, VDPHI for polar cells
  LORENTZ           Local Lorentz angle
  TIME              Total drift time
  PATH              Total drift path length
  DIFFUSION         Integrated diffusion        only if data is available
  AVALANCHE         Avalanche multipliciation   only if data is available
  LOSS              Loss due to attachment      only if data is available
  STATUS            Drift line status code      a number, not a string
  P                 Pressure of the gas
  ------------------------------------------------------------------------

  Other variables can be added on request.

contour

  Produces a plot of the lines of equal function values. The contours
  are labeled with the function value if the LABEL option is on (which
  is by default the case).

  The function is computed on the part of the viewing plane that is
  located within the current AREA box.

  If you request AUTOMATIC scaling of the range, contours are drawn
  at decent function heights covering the range of the function on the
  AREA. The number of contours is used to compute a rough distance
  between two contours; the distance is rounded downwards. The number
  of contours actually drawn may therefore be larger than the number
  you request.

  Note that much better equal time contours can be obtained with the
  DRIFT WIRE ISOCHRONES=delta NODRIFT-PLOT instruction which takes the
  end-point of the drift lines into account when deciding which points
  of the contours are to be joined with a line.

  [The default function is V, the drift velocity, and the contour range
  is by default adjusted automatically. By default, about 20 contours
  are plotted.]

graph

  The function is evaluated on the track or on the curve specified
  with the ON keyword.

  The geometric aspects of the track, if used, should be set by means
  of the TRACK command before calling PLOT. Other aspects of the track,
  such as the clustering model, are not used in the present context.

  A curve should be parametrised in terms of T which will run from 0
  to 1. All 3 coordinates of the curve should be specified. Note that
  ON expects only one argument, the parametrisation should therefore
  be enclosed in quotes, e.g. 'cos(pi*t),sin(pi*t),0' would be
  appropriate to describe a semi-circle in the z=0 plane.

  The SCALE option can be used to force a vertical scale in the
  plot, this can for instance be useful if you intend to overlay
  various graphs.

  If you select the PRINT option, then the values plotted in the
  graph will also be printed out. Output re-routing (> file) can
  be used to write the values to a file.

  The number of sampling points can be set with N, default is 200.

  [The default function is V, which in this context stands for the
  drift velocity and not for the potential !]

histogram

  The function is sampled at GRID by GRID points on the part of
  the current viewing plane that is located inside the AREA box.
  The function values are entered in an histogram.

  This kind of plot can be useful to estimate for instance the
  spread in drift time over a given region.

  The automatic search for proper binning (AUTOMATIC) uses the
  first few entries to set the range. Since the grid is scanned
  in a regular sequence, these entries are not necessarily
  representative for the entire sample, in particular if the
  number of bins is small compared to the grid size. See CALL ->
  BOOK_HISTOGRAM -> options -> AUTOMATIC for details on the
  automatic binning procedure.

  [The default function is V. The number of bins is preset to 100 and
  the range is by default chosen automatically.]

surface

  The function is sampled at GRID by GRID points on the part of
  the current viewing plane that is located inside the AREA box.
  The function values are presented as a three dimensional plot.
  The plot is first rotated by phi degrees around the z-axis and
  then tilted by theta degrees from the z-axis.

  This plot is decorative but it is generally agreed upon that it is
  hard to extract any meaningful information from it ...

  [The default function is V, i.e. the magnitude of the drift
  velocity. The default viewing angles are 30 and 60 degrees.]

vector

  This plot shows the flow of a 3-vector sampled at GRID by GRID
  points on the part of the current viewing plane that is located
  inside the AREA box. The vectors are displayed like geometrical
  objects.

  The z-component is set to 0, if not explicitely specified. For
  other than (x,y) views, this may give incorrect impressions.

  It is advisable to have roughly equal ranges in view of the scaling
  that is performed on the vectors.

  [The default functions are VDX, VDY, VDZ, i.e. the drift velocity.]

ELECTRON

  Requests drifting of electrons, not ions.

  [This is default.]

ION

  Requests drifting of ions, not electrons.

  [This is not default.]

POSITIVE

  By default, electrons are drifted with negative charge and ions with
  positive charge. If you wish to see the origin of the electrons and
  ions arriving at a given position, you may wish to reverse the sign.

  The POSITIVE option forces the charge to be positive, no matter
  whether the particle is an electron or an ion.

NEGATIVE

  By default, electrons are drifted with negative charge and ions with
  positive charge. If you wish to see the origin of the electrons and
  ions arriving at a given position, you may wish to reverse the sign.

  The NEGATIVE option forces the charge to be negative, no matter
  whether the particle is an electron or an ion.

Keyword index. Formatted on 10/11/98.